Explosive appliances with a delay mechanism



April 9, 1968 w. GUERNE 3,376,819

EXPLOSIVE APPLIANCES WITH A DELAY MECHANISM Filed Feb. 7, 1966 s Sheets-Sheet 1 April 9, 1968 v w. GUERNE 3,376,819

EXPLOSIVE APPLIANCES WITH A DELAY MECHANISM Filed Feb. 7, 1966 3 Sheets-Sheet 2 April 9, 1968 W. GUERNE EXPLOSIVE APPLIANCES WITH A DELAY MECHANISM Filed Feb. 7, 1966 3 Sheets-Sheet 3 United States Patent Ofi ice 3,376,819 Patented Apr. 9, 1968 47, 3 Claims. (Cl. 102-76) ABSTRACT OF THE DISCLOSURE A shell fuze safety device preventing the fuze firing pin from striking the detonator for a predetermined time after the shot has been fired, said device comprising the combination with retractable means for locking the firing pin of a mass of a silicone gum having a hysteresis to deformation arranged yieldingly to oppose retraction of said locking means.

The present invent-ion relates to explosive appliances with a delay mechanism, the term delay mechanism being taken in a very broad meaning and including all mechanisms liable to be incorporated in an explosive appliance (shell fuze, rocket, torpedo, mine and so on) with a viewto producing, from a given time which may be predetermined (time of starting of the projectile for instance) o undetermined, possibly of the random type (time when a projectile impinges upon an obstacle or When a mine is exploded, for instance), an operation the total time of performance of which requires a predetermined time period which constitutes the characteristic delay produce-d by the mechanism, said operation being generally the release of a locking mechanism in an explosive appliance firing system. The invention is more especially concern-ed with the fuzes of projectiles provided with a safety device preventing operation of the fuze for a predetermined time after the shot has been fired, this time corresponding, for the projectile, to a distance of travel from the gun from which it has been launched.

The chief object of the present invention is to provide an appliance of this kind which is better adapted to meet the requirements of practice than those known up to the present time.

The delay mechanism of the appliance with which the invention is concerned includes a movable member subjected, when the mechanism works, to the action of a force compelling said member to move, this movable member being further subjected to delaying means adapted to block its displacements.

The invention consists in constituting said delay producing means by an elastomer, in particular consisting chiefly of silicone gum, having a substantial hysteresis to deformation and disposed in such manner, with respect to said movable member, that the latter is compelled, during at least a portion of its displacement, to push back said elastomer by deforming it, preferably against the action of resilient means, whereby, due to the hysteresis to deformation which characterizes the elastomer in question, the movement of the movable member is delayed.

Preferred embodiments of the present invention will be hereinafter described with reference to the appended drawings, given merely by way of example, and in which:

FIG. 1 is an axial sectional view of a fuze for a gyrating projectile made according to the present invention;

FIGS. 2 and 3 show, on an enlarged scale, respectively in cross section on the line II-II of FIG. 3, and in axial section on the line IIIIII of FIG. 2, the safety device according to the present invention;

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FIGS. 4 and 5 show, in axial section, two other embodiments of such a safety device;

FIG. 6 is an axial section of still another embodiment of a safety device according to the present invention.

As shown by the drawings, the fuze comprises a firing pin 1 slidable in a fuze body 2 and adapted to come into contact, by axial displacement, with the primer of a detonator 3, said firing pin 1 being prevented from coming into contact with said primer, before the shot has been fired by a locking means element 4 retractable under the effect of accelerations brought into play when the shot is fired.

In the case, hereinafter considered, where the fuze is intended to be mounted on a projectile having a movement of gyration about its axis, locking means element 4 is preferably arranged in such manner as to retract under the action of the centrifugal force. Said element 4 advantageously consists of a U-shaped piece slidable in a diametral housing 5 provided in a plug 6 fitted in fuze body 2, firing pin 1 extending between the branches of this U-sha-ped piece and bearing through its head 1a upon the front face of said U-shaped piece 4.

In order to obtain safety along the trajectory, another locking means element 7 is adapted to cooperate with element 4 in such manner as to be kept in holding position for a given time after the shot has been fired. This element 7 is subjected, when the shot is fired, on the one hand, to the action of a force tending to move it in the direction corresponding to release of element 4, and, on the other hand, to the action of delay mean-s capable of increasing the time required for enabling movable element 7 to move, under the effect of said force, a distance sufi"1- cient to release locking means element 4.

Of course delay means for the same purpose have already been constituted by a damping liquid capable of braking the movement of the movable element of the locking device.

However, such a solution has proved to be unsatisfactory for various reasons, and in particular fo the following ones:

On the one hand, important variations of viscosity of the liquid that is used resulting from temperature variation-s produce important variations of the safety that is obtained.

On the other hand, leaks are liable to occur during the period for which the fuzes are stored, which period may be very long and during which the fuzes may be in a position for which the liquid tends to leak out despite all precautions.

The chief object of the present invention is to obviate these drawbacks, that is to say to obtain a safety which remains constant within a wide range of temperatures, said safety being uniniluen-ced by the duration of storing of the fuzes and also by the position occupied by said fuzes during said period.

It is reminded that the following characteristics are presented by some elastomers and in particular by those designated by the generic term of silicone gum elastomers, said bodies being obtained by mixing together a silicone gum (for instance Rhodorsil 13076 gum manufactured by the French firm Societ des Usines Chimiques Rhone- Poulenc, a catalyst (for instance peroxide of benzoyl in the state of a paste), a charge (for instance silica in the powder state) and possibly a coloring material and an additional body for the reduction of the rate of compres sion (mercurous oxide for instance).

Such elastomers have the following remarkable proper ties:

' They are stable, in particular from the point of view of the constancy of their physical characteristics, within a wide range of temperatures extending from 40 C. to C.

They are capable of creep deformation, but with a hysterisis to deformation, which means that, when they are subjected to the action of a force capable of deforming them, there is a lagging or retardation of the effect produced, i.e. that the deformation takes place only if the force in question is applied for a sufiicient time.

They are much less liable to leak out than liquids due to the fact that at rest they are in the state of a paste.

Finally they resist well to oxidizing and they tend to repel moisture.

Account being taken of these characteristics of elastomers consisting chiefly of silicone gum, the chief feature of the present invention consists in constituting the delay means intended to brake the movement of element 7 belonging to the locking means 4 by means of a silicone gum elastomer 8 disposed in such manner, with respect to movable element 7, that the latter is compelled, during at least part of its displacement, to drive off said elastomer by deforming it, preferably against the action of resilient means compelling said elastomer initially to occupy the whole of its housing.

It will be readily understood that this new application of silicone gum elastomer-s to a delay mechanism for a fuze gives a fully satisfactory solution of the problems involved by this kind of mechanism.

As a matter of fact, this elastomer will permit, owing to its hysteresis against deformation, of obtaining the desired delay in the displacement of movable element 7, which in turn releases element 4.

This delay will be independent of the temperatures of utilization of the fuze due to the stability of elastomer, in particular from the point of view of its plasticity, within a very wide temperature range.

Furthermore the delay mechanism will be always operative, even after the fuzes have been stored for a very long time, in any position whatever, due to the fact that the elastomer has no tendency to leak out and may be kept in its housing by ordinary means for ensuring fluidtightness, and also owing to the fact that it is not alterable by moisture.

According to a first embodiment of the invention, illustrated by FIGS. 2 and 3, the force urging movable element 7 in the release direction is a force brought into play when the shot is fired, to wit the centrifugal force, and said movable element consists of a finger mounted slidable in a radial passage provided in plug 6, one of the ends of said movable element 7 fitting along a given length in a housing provided for this purpose in element 4. One of the ends of element 7 is engaged over a given length in a housing provided in element 4 whereas the other end of element 7 projects into an axially extending variable volume chamber wherein elastomer 8 is kept under pressure by a piston 9 subjected to the action of spring 10.

The operation of such a fuze is as follows:

When the shot is fired, finger 7 tends to move radially away from element 4 while projecting into the elastomer and driving out the latter against the action of spring 10. The hysteresis to deformation of elastomer mass 8 slows down the movement of finger 7 and retards the time when the inner end of finger 7 is wholly retracted from element 4 which is then released and can in turn retract, under the effect of the centrifugal force, which permits firing pin 1 to slide rearwardly in case of impact of the projectile on an obstacle. The time necessary for clearing finger 7 from element 4 constitutes the safety of the fuze and this time can be adjusted easily and accurately when manufacturing the fuze, for instance by suitably choosing the plasticity of the elastomer or upon the relative masses of finger 7 and elastomer 8, or the length of the portion of finger '7 engaged in element 4.

According to a second embodiment of the invention illustrated by FIG. 4, movable element 7 is similarly arranged but in this case the variable volume chamber containing the elastomer extends radially and is limited by a movable wall consisting of a ring 11 slidable on finger 7 and applied against the elastomer by a spring 12 bearing against a shoulder 13 rigid with said finger 7.

With such a fuze, the delayed deformation of elastomer 8 has for its effect to push ring 11 toward shoulder 13 which itself moves toward said ring 11 under the effect of the centrifugal force, this double movement being simultaneous with a compression of spring 12 and going on until the inner end of finger 7 is wholly cleared from element 4.

According to a third embodiment, illustrated by FIG. 5, the force acting on movable element '7 is a resilient force kept out of action until the shot is fired and permitted to act only from this time on. Movable element 7 consists of a finger for locking element 4 and slidable axially under the action of spring 14 hearing against a fixed abutment and against a shoulder 15 carried by said finger 7. Shoulder 15 is temporarily kept in fixed position by a locking element 16 retracting under the effect of an acceleration produced by the firing of a shot, which accel eration permits finger 7 to move under the action of spring 14 into elastomer 8 which compresses with a given delay, as in the preceding case, a ring 17 slidable along finger 7 and subjected to the action of a spring 18 interposed between said ring 17 and shoulder 15.

According to a fourth embodiment illustrated by FIG. 6, the fuze is of the shutter type, that is to say comprises a primer 19 diametrally housed in a disc 20 kept, before the shot is fired, in a position such that primer 19 is then out of line with firing pin 1. This disc 20 has an cecentrically located center of gravity so that the centrifugal force due to the gyration of the fuze tends to swing said disc 20 into a position where primer 19 is located on the trajectory of firing pin 1.

Disc 20 is maintained in its safety position, illustrated by FIG. 6, until the shot is fired by the following means:

on the one hand, a split ring 21 preventing disc 20 from rotating as long as the centrifugal force has not caused said ring 21 to be retracted by radial expansion, and,

on the other hand, a push piece 22 bearing upon the fiat surface 20a of disc 20, said push piece being mounted slidable in the direction of the axis of fuze body 2 and being provided with an axial bore for the passage of firing pin 1.

This push piece is provided with a head 22a of enlarged diameter projecting partly into a radial bore 23 in which is fitted a piston 24 subjected to the action of a spring 25 bearing upon a plug 26 fixed in the fuze body.

The chamber into which the head 22a of push piece 22 projects is filled with elastomer 8.

Push piece 22 acts in the same manner as the holding finger 7 of the preceding embodiments. As a matter of fact, in order to enable disc 20 to pivot and to come into active position, head 22a must be pushed into the chamber occupied by elastomer 8, the hysteresis to deformation of said elastomer then producing the desired safety.

Whatever be the embodiment that is chosen, the advantages of a fuze made according to the present invention, both from the point of view of simplicity and to that of safety of operation and lack of response to the temperature of use and to the duration of storing, same as to the positions occupied during this storing, result from the above description.

It should also be noted that, owing to the fact that the elastomer is less liable to leak out than a liquid, the operations of machining the housing of said elastomer may be performed with a precision lower than in the case of a fuze where the damping element is a liquid, thus reducing the cost of the fuze.

A supplementary safety against possible leak may be obtained by housing the elastomer 8 in a resilient bag, for instance of a plastic material which will be punctured at the beginning of the operation of the delay mechanism. The device might also be arranged in such manner 5 that when it is brought into play, the elastomer is expelled through an orifice kept closed until the shot is fired.

Of course the delay mechanism according to the present invention might be applied to fuzes in order to produce an automatic destruction thereof after the projectile has travelled over a predetermined distance, or again in order to ensure a delay of the operation of the fuze for a predetermined time after an impact.

In a general manner, while the above description discloses What is deemed to be practical and eflicient embodiments of the present invention, said invention is not limited thereto as there might be changes made in the arrangement, disposition and form of the parts without departing from the principle of the invention as comprehended within the scope of the appended claims.

What I claim is:

1. In an explosive engine of the type wherein at least one of two parts, consisting of a detonator and a firing pin, is movable in a casing to strike the other part in response to an external force acting on said engine and retractable locking means operatively connected to said parts are adapted to undergo a retraction movement to release the movable part,

the combination with said locking means of a device for delaying the retraction movement thereof, consisting of a mass of deformable material housed in said casing in contact with a portion of said means so as yieldingly to oppose said retraction movement thereof, said material being an elastomer gum having a substantially complete hysteresis to deformation upon the initial impact of a predetermined force capable 0f deforming it, but deformable under the action of a force llower than said predetermined force when the latter is applied for a predetermined period of time longer than said initial impact. 2. A combination according to claim 1 wherein said material is a silicone gum elastomer.

3. A combination according to claim 2 further including resilient means for compressing said mass in its housing provided in said casing.

References Cited UNITED STATES PATENTS 2,363,562 11/ 1944 Thibodeau et al 102-79 2,721,913 10/1955 Kent 10270.2 X 2,750,890 6/1956 Leonard 102-82 2,896,540 7/1959 Voland 102-82 X 2,961,959 11/1960 Van Billiard 102-46 3,261,293 7/1966 Webb 10282 BENJAMIN A. BORCHELT, Primary Examiner. SAMUEL FEINBERG, Examiner.

G. H. GLANZMAN, Assistant Examiner. 

